Histological study of reconstructed flaps in the oral cavity

Various cutaneous flaps have been used to reconstruct intraoral defects created by tumor resection. Transplanted cutaneous flaps clinically show changes such as color changes and scaling. To better understand the biological conditions of reconstructed flaps that survive in the intraoral environment, patients in whom various periods had passed since reconstruction operations were clinically observed, and biopsy specimens taken from their flaps were examined histologically, histochemically and immunohistochemically.Seventeen major flaps, including delto-pectoral flaps, pectoral major myocutaneous flaps and forearm flaps, were used to reconstruct intraoral defects remaining after the resection of oral cancer. Irradiated flaps were excluded. Biopsy specimens were taken from both the mid-portion of each flap and the junction between the flap and the surrounding oral mucosa. Histological, histochemical and immunohistochemical examinations were performed as follows. A formalin-fixed specimen was dehydrated and embedded in paraffin. Hematoxylineosin, periodic acid-Schiff with and without diastase digestion, and alcian-blue were used to stain the deparaffinized sections of the specimens. The deparaffinized sections also underwent N-(7-dimethylamine-4-methl-3-coumarinyl) maleimide (DACM) staining to examine the distribution patterns of SH groups and SS linkages of cellular proteins in the epidermis. Immunohistochemically, frozen sections were first cut in a cryostat and stained with monoclonal antibodies. Anti-hair keratin monoclonal antibodies (HKN-2, 4, 5, 6, 7), anti-basal cell epithelioma keratin monoclonal antibodies (BKN-1), K92, and RKSE60 were used.The clinical features of cutaneous flaps seemed to depend on their location in the oral cavity rather than the period since operation or the kind of flap. Although the horny layer of the epidermis of the flaps showed thinning histologically, the epidermis showed a normal pattern of SH to SS conversion by DACM staining histochemically, as well as normal keratin expression by keratin staining immunohistochemically. The tongue epithelium adjacent to the flaps often showed flattening. Some specific keratins of the tongue epithelium were still recognized but hard keratin was not. Although cutaneous flaps may be influenced by environmental factors in the oral cavity, the flap tissues seem to retain their original cell differentiation.